Biochemistry
6th Edition
ISBN: 9781305577206
Author: Reginald H. Garrett, Charles M. Grisham
Publisher: Cengage Learning
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Chapter 26, Problem 9P
Interpretation Introduction
To write:
The chemical mechanisms for 6, 8, 9 steps of the purine biosynthesis.
Concept Introduction:
The purine is an
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In some organisms, isoleucine can be synthesized in a multi-step procedure (a series of enzymatic reactions),
beginning with a molecule of threonine. Keeping that in mind explain the experimental results below.
Amount of endproduct
Activity of threonine
(isoleucine)
deaminase
None
Low
Medium
High
Very high
High
Moderate
Very low
Fructose 1,6-bisphosphatase (FBPase) is a key enzyme in gluconeogenesis. The mammalian enzyme is tetrameric, negatively regulated by both Fructose 2,6-bisphosphate and AMP. Propose three (3) distinct models for how these molecules regulate FBPase activity. Also, describe how the enzyme might differentiate between Fructose 1,6 bisphosphate and Fructose 2,6-bisphosphate binding to the allosteric site on the enzyme with particular emphasis on amino acids comprising the allosteric binding site(s).
Dihydrofolate reductase (DHFR) is an enzyme that reduces 7,8-dihydrofolate (DHF) to
5,6,7,8- tetrahydrofolate, a step in the biosynthesis of thymidine. Methotrexate (MTX) a
structural analogue of dihydrofolate, inhibits this enzyme. MTX has been used in cancer
therapies because the inhibition of DHFR restricts thymidine production required for cell
division. In the absence of thymidine the cancerous cells cannot multiply.
Using the following data of DHFR activity in the presence of MTX,
i)
Determine the inhibition mechanism of MTX and the maximum reaction rate.
If Km for DHFR is 0.100 uM, what is K; ?
ii)
[DHF](MM)
Rate w/200 nM
Rate w/50 nM MTX
(mMs-¹)
Rate w/100 nM
MTX
MTX
(mMs ¹)
(mMs ¹)
3
7.38
5.56
3.72
6
8.84
7.38
5.55
9
9.46
8.29
6.65
12
9.79
8.84
7.38
Chapter 26 Solutions
Biochemistry
Ch. 26 - Prob. 1PCh. 26 - Prob. 2PCh. 26 - Allosteric Regulation of Purine and Pyrimidine...Ch. 26 - Inhibition of Purine and Pyrimidine Metabolism by...Ch. 26 - Prob. 5PCh. 26 - Allosteric Regulation of Ribonucleotide Reductase...Ch. 26 - Prob. 7PCh. 26 - Prob. 8PCh. 26 - Prob. 9PCh. 26 - Prob. 10P
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